Beach response due to sand nourishment on the east coast of Malaysia

Abstract

The Cempedak Bay beach stability assessment was performed by comparing the spatial and temporal pattern of beach variability before and after sand nourishment. The analysis of temporal sand volume patterns shows that the beach has lost about 6% or 10 000 m³ volume of sand which is equivalent to 4m³/m per year from the nourishment zone over the 2·5-year monitoring period. The present shoreline recession rate is established to be 1.7 m/year (valid for data set of March 2005 to July 2007). The analysis of seasonal changes is assessed through temporal beach volume patterns, which indicate that shoreline variability can be characterised by an alongshore rhythmic pattern of alternating seasonal behaviour. A simple seasonal transport pattern is proposed to account for alternating erosion and accretion. The temporal distribution pattern of beach level changes reveals the existence of a nodal point around 40 to 50 m offshore, which is influenced by the monsoonal system. The spatial distribution of the beach width indicates that the northern beach area is wider whereas the southern beach area experiences lower beach width, which is coincident with the temporal pattern of sand volume and beach profile changes. A slight beach rotation does exist attributed to a seasonal or periodic shift in wave climate, in particular wave direction. The planform stability of the beach is tricky to determine due to model uncertainties, especially the selection of the diffraction point. This baseline study is important towards the development of a process-based model in order to investigate the morphological nearshore behaviour of headland bay beaches.